JPH04237931A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To make focus regulation from low luminance to high luminance in CRT by using one variable resistor. CONSTITUTION:In a CRT equipped with more than 3 quadrupole lenses, the positive electrode of a first quadrupole lens Q1 and the positive electrode of a second quadrupole lens Q2 are connected to a fixed power supply terminal 43, and a part of the negative electrode of the first quadrupole lens Q1 and a part of the negative electrode of the second quadrupole lens are connected to a common variable resistor 24. The remaining negative electrode of the second quadrupole lenses is connected to the fixed power supply terminal 46.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to observation CRTs (cathode ray tubes) used in oscilloscopes and the like.

0002

[Prior art and problems to be solved by the invention] Cathode,
A control electrode, an accelerating electrode, unipotential type first and second quadrupole lenses, a vertical deflection system, a unipotential type third quadrupole lens, a horizontal deflection system, a scanning magnifying lens, and a screen on the axis of the exhaust pipe body. Configuring the CRT of an oscilloscope by arranging the CRT along
It is disclosed in Japanese Patent Application Laid-open No. 64-6348.

The imaging principle in these CRTs can be shown in FIG. In FIG. 1, first, second and third quadrupole lenses Q1, Q2, Q3 are arranged on the tube axis 1. In FIG. 1, the vertical lens action (focus state) is displayed in the upper region 2 of the tube axis 1 from the object point 12 (crossover) toward the image 5 on the image plane 4, and the horizontal lens action is shown in the lower region 3. (Focus status) is displayed. first and third quadrupole lenses 6 denoted by Q1 and Q3;
8 acts as a concave lens in the vertical direction and a convex lens in the horizontal direction, and the second quadrupole lens 7 shown by Q2 acts as a convex lens in the vertical direction and a concave lens in the horizontal direction. By providing the three quadrupole lenses Q1, Q2, and Q3 in this manner, the image 5 can be made close to a perfect circle.

An object point 12 in FIG. 1 indicates that electrons emitted from the cathode 9 shown in FIG.
This is a point (crossover) that is converged to approximately one point by the lens formed by the above.

The distance from the object point 12 (crossover) to the first quadrupole lens Q1 is v, and the first quadrupole lens Q1 is
d is the distance from the second quadrupole lens Q2 to the third quadrupole lens Q3, q is the distance from the second quadrupole lens Q2 to the third quadrupole lens Q3, z is the distance from the third quadrupole lens Q3 to the image plane 4, and each quadrupole Assuming that the focal lengths of the concave and convex surfaces of the lenses Q1, Q2, and Q3 are the same, the reciprocals of the concave and convex focal lengths of the lenses are S1, S2, and S.
3, then S1, S2, and S3 are expressed as (1) (
2) It can be expressed by equation (3).

[0006]

[Math 1]

In FIG. 2, when the voltage of the control electrode 10 is changed to control the amount of electron beam, the position of the object point 12 changes. That is, from the object point 12 to the first quadrupole lens Q1
The distance v changes. This means that unless the lens constant of each quadrupole lens is changed according to the change in v, the image 5 will not be formed on the image plane 4. One of the weaknesses of electron guns using quadrupole lenses is the complexity of adjusting the voltage of each quadrupole lens when changing the amount of electron beam. A method to solve this complexity is disclosed in the above-mentioned Japanese Patent Application Laid-open No. 63-237333.
It is disclosed in the publication No.

However, in these CRTs, at least two variable resistors must be adjusted in response to changes in the amount of electron beam.

[0009] Japanese Unexamined Patent Publication No. 63-237334 states,
As shown in principle in FIG. 3, an axially symmetrical lens 13 is arranged between the object point 12 and the first quadrupole lens Q1, and the position of the object point 12 is made substantially constant by the action of the lens. is disclosed. In FIG. 3, it is assumed that the distance between the axially symmetrical lens 13 and the first quadrupole lens 13 is e, and the position of the object point changes from v to v' by adjusting the control electrode 10. When this is returned to v by the action of the axially symmetrical lens 13, the size of the object point becomes (v-e)/(v'-
e). When increasing the amount of electron beam, the relationship v>v' holds. Therefore, when the beam amount is increased, the object point 12 is enlarged by the action of the axially symmetrical lens 13. In this example, the axially symmetrical lens 1 corresponds to the change in the control electrode 10.
By adjusting only voltage 3, image formation 5 can be obtained without changing the others. However, when the beam amount is increased, the object point 12 becomes larger, the image formation 5 becomes larger, and the quality deteriorates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a CRT in which changes in the focus state due to changes in the amount of electron beam can be adjusted using a single variable voltage source.

[0011]

Means for Solving the Problems The present invention to achieve the above object provides a cathode ray tube having at least first, second and third quadrupole lenses, in which at least the first and second quadrupole lenses are each comprising a plurality of plate-shaped electrodes arranged perpendicular to the axis, the plurality of plate-shaped electrodes applying a voltage of a first polarity to a plurality of first polarity electrodes and a plurality of electrodes of a second polarity to which a voltage of a second polarity is applied. the first polarity electrode of the first quadrupole lens and the first polarity electrode of the second quadrupole lens are connected to the same voltage source; The second polar electrode of the first quadrupole lens and a part of the second polar electrode of the second quadrupole lens are connected to the same variable voltage source, and the second polar electrode of the second quadrupole lens is connected to the same variable voltage source. This relates to a cathode ray tube characterized in that the remaining portions are connected to another voltage source.

0012

[Operation] A part of the second polar electrode of the second quadrupole lens
By applying the same voltage as the quadrupole lens, the second
An effect equivalent to changing the lens length of the quadrupole lens occurs. The contribution of the change in the lens length of the second quadrupole lens to the lens constant is used to correct the change in the focus state due to the change in the amount of electron beam. As a result, focus adjustment down to low brightness can be performed with one variable voltage source.

[0013]

Embodiment Next, a CRT for an oscilloscope according to an embodiment of the present invention will be described. FIG. 4 shows a cathode 9 arranged along the tube axis 1, a control electrode 10, an accelerating electrode 11, first and second unipotential quadrupole lenses Q1,
Q2, a vertical deflection system 40 consisting of a pair of deflection plates, a third unipotential quadrupole lens Q3, a horizontal deflection system 41 consisting of a pair of deflection plates, and a dome mesh 42.
A CRT is shown comprising an image plane or screen 4. Note that the exhaust pipe body of the CRT is omitted. Since the basic structure and operation of each part are substantially the same as those disclosed in Japanese Patent Application Laid-open No. 63-237334, detailed explanation will be omitted.

The dome mesh 42 is formed to have axial symmetry, has the function of focusing the image point formed on the image plane 4 on the screen surface, and furthermore has the function of focusing the image point formed on the image plane 4 on the screen surface. It has the function of expanding the beam (scanning expansion function).

[0015] First, second and third quadrupole lenses Q1,
Q2 and Q3 consist of a combination of a first electrode 20 shown with hatching for convenience of explanation and a second electrode 21 shown without hatching. In this embodiment, the first and second quadrupole lenses Q1 and Q2 are each constructed by alternately arranging three first electrodes 20 and three second electrodes 21, and the third quadrupole The first electrode 20 has two lenses Q3.
and two second electrodes 21 are arranged alternately. . In addition, each quadrupole lens Q1, Q2
, Q3, in order to obtain the lens action shown in FIG.
2 is different. That is, in the first and third quadrupole lenses Q1 and Q3, the first electrode 20 is a positive polarity (first polarity) electrode, and the second electrode 21 is a negative polarity (second polarity) electrode.
In the second quadrupole lens Q2, the second electrode 2
1 is a positive polarity electrode, and the first electrode 20 is a negative polarity electrode.

FIG. 5 shows the electrode 20 of the first quadrupole lens Q1.
, 21, and the center of each electrode 20, 21 coincides with the tube axis 1. Each electrode 20, 21 is spaced l
are arranged parallel to each other and at right angles to the tube axis 1. The total length of this lens is L.

FIG. 6 is a perspective view showing the first and second electrodes 20, 21 in detail. The first and second electrodes 20 and 21 made of metal plates have holes 20a and 21a, respectively. Hole 2
0a and 21a are a pair of peripheral edges 2 protruding toward the axis 1
2, and a pair of peripheral edges 23 that are recessed away from the axis 1.
and respectively. A pair of peripheral edges 22 arranged symmetrically around the tube axis 1 are expressed by the formula x2 −y2 = ±a, which indicates a rectangular hyperbola.
It has a curvature that almost satisfies 2. Similarly, a pair of peripheral edges 23 arranged symmetrically around the tube axis 1 represent a circle using the formula x2
It has a curvature that approximately satisfies +y2 =b2. In addition,
The relationship between the distance a from the center of the xy coordinates, that is, the tube axis 1, to the apex of the first pair of circumferential edges 22 and the distance b from the center to the apex of the second pair of circumferential edges 23 is b>a. Further, the hole 21a of the second electrode 21 is 90
It differs from the one rotated by a degree.

In this embodiment, the first and second electrodes 20
, 21 are each 0.5 mm thick, the hyperbolic constant a is 5, and the electrode spacing l is 1 mm.

In FIG. 4, the first quadrupole lens Q1
three first electrodes 20 and a second quadrupole lens Q2
The three second electrodes 21 of the first quadrupole lens Q1 are connected to the +300V power supply terminal 43.
and the first electrode 20 of the second quadrupole lens Q2 are connected to the variable resistor 44. This variable resistor 44 is connected to a negative power supply terminal 45, and applies a negative voltage of, for example, about -300V to the line 44a. Second quadrupole lens Q2
The second first electrode 20 of is connected to a negative power terminal 46 of -40V. 2nd quadrupole lens Q3
The two first electrodes 20 are connected to a +250V positive power supply terminal 47, and the two second electrodes 21 are connected to ground. A third quadrupole lens Q3 is used to reduce the number of power supplies.
Although no positive and negative symmetrical voltages are applied to (250
+0)/2=125, positive voltage +125V and negative voltage -1
The same effect as applying 25V can be obtained.

In FIG. 4, the axial lengths L1, L2 of the first, second and third quadrupole lenses Q1, Q2, Q3
, L3 are 10 mm, 7.5 mm, and 6 mm,
The distance v from the crossover (object point) to the center of the first quadrupole lens Q1 is 30 mm, and the first quadrupole lens Q1
The distance d from the center of Q2 to the center of the second quadrupole lens Q2
is 30 mm, the distance q from the center of the second quadrupole lens Q2 to the center of the third quadrupole lens Q3 is 60 mm, and the third
The distance z from the center of the quadrupole lens Q3 to the image plane 4 is 1
It is 20mm.

Next, by changing the voltage of the control electrode 10 to change the amount of electron beam, the focus shift caused by the movement of the crossover can be corrected using a single variable resistor.
Explain that it can be adjusted.

Lens constant S of each quadrupole lens Q1, Q2, Q3 given by the above equations (1), (2), and (3)
1, S2, and S3, the following equations (4) and (5) are obtained.

[0023]

[Math 2]

By adjusting the voltage of the control electrode 10, the distance from the crossover to the center of the first quadrupole lens Q1 is set to v.
If it changes from v - Δv, then the differential coefficient S1' of v of S1, S2, S3 corresponds to equations (4) and (5).
(v), S2'(v), and S3'(v) (6), (
7) Equation is obtained.

[0024]

[Math 3]

Equations (6) and (7) assume that v is constant and Q1
, Q2 , Q3 lens constant ratio (4), (5)
Even if it is determined by the formula, if there is a change in v, it means that the image will not be formed at the image point. That is, from equations (6) and (7), -△v
Due to the addition factor due to the change in , the equations (4) and (5) deviate from each other, and the imaging conditions are no longer satisfied. The aforementioned Japanese Patent Application Publication No. 1983
In the method disclosed in Japanese Patent No. 237334, there is no problem when v does not change much, but when v changes greatly, that is, when the beam current is increased, imaging becomes impossible.

The reciprocal S of the focal length of the quadrupole lens shown in FIGS. 5 and 6 is given by the following equation (8). In addition, V in the following formula is a positive and negative voltage applied to the electrodes 20 and 21,
L is the lens length.

[0027]

[Math 4]

This equation (8) can be calculated by appropriately selecting the lens length L to obtain S1 and S2 that satisfy equations (4) and (5).
, S3. That is,
Lens length L1 of the first quadrupole lens Q1 and lens lengths L2, L3 of the second and third quadrupole lenses Q2, Q3
Based on equations (4), (5), and (8), the following (9
), it may be determined according to equation (10).

[0029]

[Math 5]

When the lens lengths L1, L2, and L3 of each quadrupole lens Q1, Q2, and Q3 are set to satisfy equations (9) and (10), and the crossover is constant, that is, when v is constant, each quadrupole Lens Q1, Q2, Q3
An image can be formed by applying a voltage of ±V to . However, when the crossover point, that is, v changes, an additional factor is added as shown in equations (6) and (7), and the image is no longer formed on the image plane. In other words, if the lens length is determined by equations (9) and (10), the image will not be formed on the image plane, the quality of the image point will deteriorate, and it will deviate from the optimum focus.

The present invention provides a method by which the above-described focus shift can be adjusted using a single power source. The principle of the present invention basically takes into account the additional factors in equations (6) and (7). FIG. 7 explains the principle. The lens lengths of the quadrupole lenses Q1, Q2, and Q3 are L1, L2, and L3, respectively. Each of the quadrupole lenses is composed of an electrode having a hyperbolic electron passage hole shown in FIG. . That is, the quadrupole lenses Q1 and Q in FIG.
2, Q3 are quadrupole lenses Q1, Q2, Q3 in Fig. 7
is shown as well. However, the number of electrodes 20 and 21 is increased or decreased appropriately. three quadrupole lenses Q1,
Q2 and Q3 are connected to a common positive power supply terminal 30, but are not all commonly connected to a negative power supply. Parts of the second and third quadrupole lenses Q2 and Q3 are connected to the negative power terminal 31, and the rest are connected to the variable resistor 34 together with the first quadrupole lens Q1. The variable resistor 34 is connected to the negative power supply terminal 33 and applies a negative potential to the output line 34a. The lens lengths ΔL2 and ΔL3 based on the electrodes connected to the variable resistor 34 of the second and third quadrupole lenses Q2 and Q3 are as follows (11
) and (12) are set so as to satisfy the equation.

[0032]

[Math 6]

Positive and negative voltages are alternately applied to each electrode constituting the quadrupole lens, and the positive side electrode is supplied with + by the power supply 30.
V is applied. When the crossover point, that is, v is constant, -V is applied to the divided voltage output line 34a of the variable resistor 34, and -V is also applied to the power supply terminal 31. When the distance from the object point 12 to the first quadrupole lens Q16 is v, +V on the positive side
, it is clear from the above explanation that an image can be formed on the image plane 4 by applying -V to the negative side.

Next, when v changes to v - Δv, Δv
is small compared to the geometric quantities v, d, q, and z, but the amount of change S1'(v) in the lens constant S1 is S1 (v-△v
)=S1 (v)-S1'(v) Δv is derived from the equation. Therefore, the voltage △ corresponds to the amount of change in S1'(v)△v.
Assuming that V changes, the voltage applied to the first quadrupole lens changes from ±V to ±V (V+ΔV). Also, when keeping +V constant, the negative side voltage is -V (1-2ΔV)
becomes. However, ΔV is an adjustment voltage of the first quadrupole lens corresponding to a change in −Δv. That is, the above is S1
This means that (v-△v) almost matches L1 (V+△V)/a2. Since this voltage is applied to the portion of the second quadrupole lens Q2 corresponding to the lens length ΔL2, the contribution of the lens length ΔL2 to the lens constant S
' can be expressed by the following equation (13).

[0035]

[Math 7]

The contribution S'' of the second quadrupole lens Q2 before v changes is expressed by the following equation (14).
The sum S2 of 2' and S2'' is expressed by equation (15).

[0037]

[Math. 8]

Equation (15) includes equation (6). That is,
This means that even if the distance v changes due to a change in the object point 12, the focus condition can be satisfied. The same effect as that of the second quadrupole lens Q2 occurs with the third quadrupole lens Q3. Therefore, focus adjustment can be performed using one variable resistor 34. The above explanation does not take into account the effects of the ends of the quadrupole lens in order to make the explanation easier to understand. In reality, the lens length is determined experimentally or by numerical calculation, but the basic idea remains the same.

Although FIG. 4 showing the embodiment of the present invention and FIG. 7 showing the principle are not the same, the principle of focus adjustment is completely the same, and the structure of FIG. 4 allows focus adjustment. In FIG. 4, the negative potential of the output line 44a of the variable resistor 44 is -300V when the brightness is low, that is, when the beam current is small. At this time, the second quadrupole lens Q2
The lens length ΔL2 based on the electrode connected to the line 44a among the electrodes is approximately . It is 1.9mm. L2 is 7.
Since it is set to 5 mm, the ratio ΔL2 /L2 to this L2 is 0.25. On the other hand, the additional factor v(q+z)/{2d(v+q+z+d)+v in equation (6)
(q+z)} is 0.273. In this example, (6
) is slightly different from the formula, but the screen current is 20 μA.
(Equivalent to 1 mA when converted to beam current) It became possible to adjust the focus. Estimating from equation (1), the change in v at this time is about 8 mm.

[0038]

[Modifications] The present invention is not limited to the above-described embodiments, but can be modified, for example, as follows. (1) The negative potentials of the first and second quadrupole lenses Q1 and Q2 are set to the same or fixed, and the second quadrupole lens Q2
The first one is selected from the electrodes that should give a positive potential of
The quadrupole lens Q1 may be connected to a positive variable voltage source together with an electrode that provides a positive potential. (2) In place of the dome mesh 42, which is an axially symmetrical post-acceleration method, the CRT uses a post-acceleration method using a meshless lens such as a box-type scanning magnifying lens, which is well known in Japanese Patent Application Laid-Open No. 63-237334. The present invention can be applied. When using a meshless lens, the distance to the image plane is different in the horizontal and vertical directions. Therefore (1),
Although equations (2) and (3) are modified, similar relational equations can be obtained. That is, an additional factor is calculated in the same manner as the method explained in the embodiment, and one or both of the second quadrupole lens Q2 and the third quadrupole lens Q3 is divided so as to correspond to this additional factor. A similar result can be obtained by connecting Q1 to the first quadrupole lens Q1.

[0039]

As described above, focus adjustment from low brightness to high brightness can be performed with one variable voltage source.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the principle of image formation using three quadrupole lenses by optical analogy.

FIG. 2 is a diagram showing the generation of an object point by a lens system consisting of a cathode, a control electrode, and an accelerating electrode of a CRT.

FIG. 3 shows a lens system with an axially symmetric lens.

FIG. 4 is a diagram showing the principle of a part of a CRT according to an embodiment of the present invention.

FIG. 5 is a diagram showing the first quadrupole lens of FIG. 4;

FIG. 6 is a perspective view showing the first and second electrodes of FIG. 5;

FIG. 7 is a diagram showing three quadrupole lenses for explaining the principle of the present invention.

[Explanation of symbols]

1 Tube shaft 4 Image plane 9 Cathode 10 Control electrode 11 Accelerating electrode 44 Variable resistor Q1, Q2, Q3 Quadrupole lens

Claims (1)

[Claims] 1. A cathode ray tube having at least first, second, and third quadrupole lenses, wherein at least the first
and a second quadrupole lens each consisting of a plurality of plate-shaped electrodes arranged perpendicularly to the tube axis, and the plurality of plate-shaped electrodes include a plurality of first polarity electrodes to which a voltage of a first polarity is applied; the first polarity electrode of the first quadrupole lens and the first polarity electrode of the second quadrupole lens have the same voltage. the second polar electrode of the first quadrupole lens and a portion of the second polar electrode of the second quadrupole lens are connected to the same variable voltage source; A cathode ray tube, wherein the remainder of the second polarity electrode is connected to another voltage source.